Dude what are you doing, you can't just put it in there without any other code and expect it to do exactly what you want it to do. also you need an actual IP address...
make it a function and have the client call the function when they want to switch servers, or get a derma menu and a button to make the player join the server.
On top of that, sendlua is a server side function. No need for it on the client side.